The present invention relates to an injection molding die in which molding material is fed to a molding cavity via a gate. More specifically, the injection molding die is equipped with a valve gate which includes a valve pin or the like for opening and closing the gate.
An example of an injection molding die is shown in FIG. 3. This injection molding die 31 includes: a first die 34 having a gate 37; a second die 50 forming, together with the first die 34, a molding cavity 55 that communicates with the gate 37; a manifold 40 having a molding material supply path 42 that communicates with the gate 37; and a valve gate 56 disposed at the connection between the supply path 42 of the manifold 40 and the gate 37 of the first die 34.
The valve gate 56 includes: a roughly cylindrical main valve unit 57; a valve pin 58 inserted through the main valve unit 57 and opening and closing the gate 37 of the first die 34; and a heater 59 mounted on the outer perimeter of the main valve unit 57 and heating the main valve unit 57. The end of the main valve unit 57 abuts the perimeter edge of the gate 37 of the first die 34, and the rear end of the main valve unit 57 abuts the perimeter edge of the opening of the supply path 42 of the manifold 40, thus connecting the supply path 42 and the gate 37. In this configuration, the valve gate 56 is formed as a single, integral unit from the main valve unit 57, the valve pin 58, and the heater 59.
In injection molding die 31, the main valve unit 57, the valve pin 58, and the heater 59 are a single, integral unit valve gate 56. Thus, the individual elements of the valve gate 56 must be fitted to work with each other. As a result the structure of the valve gate 56 and the attachment structures for the valve gate 56 become complex. This results in more processing and assembly operations with respect to the valve gate 56, increasing its overall price. Furthermore, a complex structure is required for sealing the valve gate 56 itself to the section where the valve gate 56 attaches to the die. This also increases processing and assembly costs, which leads to higher prices overall.
An object of the present invention is to overcome the conventional problems described above. Accordingly, the present invention provides an injection molding die that simplifies the structure of the valve gate; the structures that attach the gate and the die; processing and assembly of the gate and the die; and the sealing section structure, all of which should keep the overall price of the die and gate lower.
Accordingly, the invention provides an injection molding die which comprises: a first die with a gate; a second die forming, together with the first die, a molding cavity that communicates with the gate; a manifold comprising a molding material supply path communicating with the gate; a thermal insulation space disposed between the first die and the manifold; and a valve gate disposed between the first die and the manifold, which opens and closes the gate. The valve gate comprises: a valve pin that passes through the first die and the manifold and which opens and closes the gate; a sealing member mounted on the manifold where the valve pin passes through, which provides a seal between the manifold and the first die; and a heater mounted on the manifold to heat molding material that flows through the supply path.
The valve pin opens the gate so that the molding material flows through the supply path of the manifold and is supplied to the molding cavity. The opening of the manifold should be sealed with the sealing member, which also may seal the connection between the manifold and the first die. The molding material flowing through the supply path of the manifold may be heated by the heater.
In a further embodiment, the sealing member comprises a pressure-receiving section at an area facing the supply path of the manifold; and a seal is made between the manifold and the first die as a result of pressure from the molding material flowing through supply path that is received by the pressure-receiving section. The pressure from the molding material flowing through the supply path in the manifold acts on the pressure-receiving section of the sealing member. This results in pressure to the sealing member, providing a seal between the manifold and the first die.